Integrated circuit memory devices are widely used in consumer and commercial systems. As is well known, memory devices may be tested in various manners using several test parameters for determining whether they operate properly. However, a memory device whose cells are partly defective can be used normally if the defective cells are replaced with redundancy memory cells. The memory cells and the redundancy memory cells are connected to control circuits through fuses. Thus, if there is a defective memory cell, the fuse connected to the defective memory cell may be blown. Then, the redundancy memory cells are driven so that the defective memory cells are replaced with the redundancy memory cells.
Fuses for use in memory devices include electrical fuses blown by electricity and laser fuses blown by a laser beam. Electrical fuses arc typically used in Electrically Erasable and Programmable Read Only Memory (EEPROM) devices and laser fuses are typically used in Dynamic Random Access Memory (DRAM) devices.
FIG. 1A is a layout arrangement diagram in a laser fuse box of a conventional integrated circuit memory device. Referring to FIG. 1A, laser fuses 111 through 116, used in a conventional memory device 101, have uniform widths W1 and pitches P1. Central portions 131 of the laser fuses 111 through 116 are blown by a laser.
As shown in FIG. 1A, if the pitches P1 of the laser fuses 111 through 116 are each the same, reducing the size of the memory device 101 may reduce the pitches P1 of the laser fuses 111 through 116 accordingly. If the pitches P1 of the laser fuses 111 through 116 are reduced, laser fuses adjacent a specific laser fuse to be blown may be damaged.
FIG. 1B is another layout arrangement diagram in a laser fuse box of a conventional memory device, which is disclosed in U.S. Pat. No. 5,747,869 to Prall et al. Referring to FIG. 1B, laser fuses 151 through 156 have narrow ends 151a through 156a, and wide ends 151b through 156b. Spaces S1 and S2 are beside the narrow ends 151a and 156a of the laser fuses 151 and 156, as shown in FIG. 1B. As the size of integrated circuit devices continues to decrease and the number of devices incorporated into integrated circuit devices continues to increase, it may be desirable to increase the laser fuse density. It also may be desirable to increase the laser fuse density without the need to reduce the pitch between fuses.